Balloon catheters are in widespread use for effecting various medical treatments, including vascular dilatation, angioplasty, vascular occlusion and also for deploying implantable medical devices.
It is highly advantageous for the balloons of such assemblies to be made of a material and form that they can be wrapped or folded onto the carrier catheter to as small a diameter as possible. Moreover, it is important for such balloons to be made of a material which can withstand the pressures to which they are inflated and the rigors of the medical treatment. As a result of these requirements, medical balloons tend to be made of a thin and strong material. Examples include polyamide (e.g. nylon), polyether block amide (e.g. Pebax®), PET, polyethylene and polyurethane.
These materials form good balloon structures but are very difficult to detect when deployed in a patient. The use of fluoroscopy, X-rays or CRT techniques can improve the visibility of these balloons when in the patient's body but are not optimal techniques. Ultrasonic imaging is a medically preferred technique but not ideal for imaging balloons or balloon catheters, which are in some cases invisible. Attempts have been made to provide such balloons with an element which gives them echogenicity or radiopacity. A common route is to use contrast media to inflate the balloon. While contrast media does enable the balloon to be readily visible by ultrasonic imaging, this is only once the balloon has been inflated; with no contrast media the balloon remains invisible. Moreover, contrast media is relatively viscous, which results in slower inflation and deflation times and also in a limit to the minimum diameter of the inflation and/or deflation lumen which can be used for injecting and/or removing the contrast media into or from the balloon. This also dictates a minimum size of catheter which can be used with these arrangements. Furthermore, contrast media is not particularly biocompatible, leading to risks of medical complications should there occur loss of contrast media into the patient's body, for instance as a result of balloon burst.
Balloon catheter assemblies which include one or more radiopaque and/or echogenic features have been disclosed in U.S. Pat. No. 3,228,894, U.S. Pat. No. 4,702,252, U.S. Pat. No. 5,300,048, U.S. Pat. No. 5,948,489, U.S. Pat. No. 6,540,721, U.S. Pat. No. 6,652,568, U.S. Pat. No. 6,761,708, US-2004/181,252, US-2008/045,893, US-2009/306,589 and US-2009/306,769.